A new and more powerfully activating diamine for practical and scalable enantioselective aldehyde crotylsilylation reactions

Abstract

A new diaminophenol ligand for crotylsilylation reactions with cis- and trans-crotyltrichlorosilane has been developed. The conformational constraints that result from the tethering of the phenol to one of the amino groups attenuate the stereoelectronic effects that reduce activity in the corresponding untethered diaminosilanes, and the resulting crotylsilane reagents are as active as our previously reported EZ-CrotylMix reagents, but without requiring the use of the Sc(OTf)₃ catalyst. In turn, this has allowed the development of an experimentally straightforward, sustainable, efficient, and scalable one-pot procedure which may be carried out in ≤8 hours, and in which the diaminophenol activator ligand may be easily recovered in ≥90% yield by recrystallization.